The researchers have analyzed data from 200 earthquakes of magnitude 6 or greater in the past decade.
Data obtained from seismic waves caused by earthquakes have shed new light on the deepest parts of the Earth’s inner core.
By measuring the different speeds at which these waves penetrate and traverse the inner core of the Tierra, researchers of the ANU (Australian National University) they believe they have documented evidence of the existence of a distinct layer within the Earth known as the deepest inner core: a solid “metal ball” found at the center of the inner core.
Until recently it was thought that the structure of the Earth was made up of four distinct layers: the crust, the mantle, the outer core, and the inner core. The findings, published in Nature Communications, confirm the existence of a fifth layer.
“The existence of an inner metallic ball within the inner core, the innermost core, was hypothesized about 20 years ago. Now we bring another line of evidence to prove the hypothesis,” declared the doctor Thanh-Son Pham, from ANU Research School of Earth Sciences.
The teacher Hrvoje Tkalcic, also from the ANU, said that studying the deep interior of Earth’s inner core can tell us more about the past and evolution of our planet.
“This inner core is like a time capsule of Earth’s evolutionary history: it is a fossilized record that serves as a gateway to events from our planet’s past. Events that occurred on Earth hundreds of millions or thousands of years ago. millions of years,” he explained.
The researchers analyzed the seismic waves that travel directly through the center of the Earth and “spit” them out on the opposite side of the globe to the place where the earthquake was triggered, also known as the antipodes. The waves then return to the origin of the seism.
The ANU scientists describe this process as similar to the bounce of a ping pong ball.
“By developing a technique to augment the signals recorded by densely populated seismograph networks, we have observed, for the first time, seismic waves that bounce back and forth up to five times along the diameter of the Earth. Previous studies had only documented a single antipodal rebound,” says Dr. Pham.
“The findings are exciting because they provide a new way to probe Earth’s inner core and its most central region.”
One of the earthquakes studied by scientists it originates from Alaska. The seismic waves caused by this quake “bounced” somewhere in the South Atlantic, before traveling back to Alaska.
The researchers studied the anisotropy of the iron and nickel alloy that makes up the interior of the Earth’s inner core. Anisotropy is used to describe how seismic waves speed up or slow down through Earth’s inner core material depending on the direction in which they travel. It could be due to the different arrangement of the iron atoms at high temperatures and pressures or to the preferential alignment of the growing crystals.
They found that the rebounding of seismic waves repeatedly probed points near the center of the Earth from different angles. By analyzing the variation in travel times of seismic waves in different earthquakes, scientists deduce that the crystallized structure of the innermost region of the inner core is probably different from that of the outer layer.
They claim this could explain why waves speed up or slow down depending on their angle of entry as they enter the innermost nucleus.
According to the ANU team, the findings suggest that at some point in Earth’s evolution there may have been a major global event that caused a “significant” change in the crystalline structure or texture of Earth’s inner core.
“There are still many unanswered questions about Earth’s innermost core, which could hold the secrets to unlocking the mystery of our planet’s formation,” said Professor Tkalcic.
the researchers analyzed data from about 200 earthquakes of magnitude 6 or greater of the last decade.
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